The present invention relates to a method and a system for controlling robot arms of automatic guided vehicles on a semiconductor wafer production line, wherein the individual automatic guided vehicles perform accurate operations of loading and unloading a semiconductor wafer carrier onto and from predetermined placement positions of plural stations possessed by manufacturing equipment and automatic wafer stack on the semiconductor wafer production line.
The individual automatic guided vehicle is computer-controlled to stop in front of loading-purpose or unloading purpose station of the manufacturing equipment or loading/unloading-purpose station of the automatic wafer stack for subsequent operations of the robot arm provided on the automatic guided vehicle under computer-control for loading and unloading the wafer carrier onto and from the stations.
Actually, however, any trouble may accidentally appear on the automatic guided vehicle with the robot arm. In this case, it is of course necessary replace the troubled one of the practically working automatic guided vehicles by a stand-by automatic guided vehicle. Alternatively, any periodic inspection to the practically working automatic guided vehicles is necessarily needed. In this case, it is also needed to replace the practically working automatic guided vehicles by reserved stand-by automatic guided vehicles. In this case, it is proposed to teach the stand-by automatic guided vehicle, about stop-position and relative-positional data before entry into the practical orbit for practical operations of loading and unloading the wafer carrier onto and from the stations. This technique is, for example, disclosed in Japanese laid-open patent publications Nos. 60-238911 and 62-191904. The provisional teaching to the stand-by automatic guided vehicle about the stop-position and relative-positional data is preferably carried out before entry into the practical orbit for practical operations of loading and unloading the wafer carrier onto and from the stations. It has been known in the art in the field of computer-control of mechanical robots. The teaching may be carried out under the same conditions as the practically working conditions. This technique is, for example, disclosed in Japanese laid-open patent publications Nos. 62-264883 and 61-30388. Further, it was proposed to compensate the displacement in the relative position between the robot and the work station before the high accurate working operation of the robot is started. This technique is also disclosed in Japanese laid-open patient publication No. 4-48304.
In view of realizing higher accurate or exactly accurate loading and unloading operations of the robot arm of the automatic guided vehicle, it is essential to solve the problem with instrumental errors necessarily and unavoidably caused in assembling the individual automatic guided vehicles provided with the robot arms. Those instrumental errors are different between individual automatic guided vehicles provided with the robot arms. For obtaining the higher accurate or exactly accurate loading and unloading operations of the robot arm of the automatic guided vehicle, the instrumental error is influence on a relative position between the hand of the robot arm and a reference point on the automatic guided vehicle to be referred for stopping the automatic guided vehicle at a predetermined stop position in front of the at least practical station. The above prior arts along or in combination could never reach any settlement for individually and exactly compensation to variable differences in individually different instrumental errors between the automatic guided vehicles.
In the above circumstances, it had been required to develop a novel method or system of realizing highly and exactly accurate operations of loading and unloading the wafer carrier onto and from stations freely from the individually different instrumental errors of the automatic guided vehicles provided with the robot arms.